LED provides higher energy utilization efficiency and longer life span, and an LED lamp set generates higher brightness on the same amount of electric power, thus is widely adopted on various types of applications to replace the conventional lighting bulbs, such as flashlights, traffic lights, vehicle lighting fixtures and the like. It also is gradually being adopted as a lighting source in general households and formed in a profile like the ordinary lighting bulb but with LEDs as the lighting source. For instance, R.O.C. patent No. M264797 entitled “Lighting bulb equipped with LEDs” provides a plurality of plates (circuit boards) surrounded like a post. Each plate has at least one LED. A lamp head is provided to connect to electric power and hold a control circuit which is electrically connected to the plates to drive the LEDs to emit light. The outer end of the lamp head further is fastened to a lamp shade encasing the plates and LEDs to be formed in a profile like an ordinary lighting bulb. The surrounded plates form a polygon. The LEDs are located on the plates to emit light in a radial manner. Due to the light generated by the LED is directional rather than in all directions like the incandescent lamp or fluorescent lamp, the area where the LED is not directly illuminating has a significant brightness difference. If the LEDs are not arranged densely, light beams are spaced from each other notably. Such a phenomenon seriously affects its acceptance to the general users.
Many techniques have been proposed in prior arts or developed to improve light beam density of lighting bulbs by deploying more LEDs. Such an approach increases the cost and power consumption, and waste heat also is increased during lighting. Moreover, increase of waste heat affects the life span and stability of the lighting bulb. In addition, the junction of two neighboring plates cannot hold the LEDs, hence a notable dark area is formed between the two plates. Furthermore, the plates used by aforesaid conventional technique are formed in a preset specification to couple the LEDs. In the event that customers request different specifications (such as different watts or sizes), the design of the plates has to be changed to meet the new requirements. As a result, design and production costs are increased.
Hence the conventional techniques still leave a lot to be desired, especially on lighting effect and production, and the problem of uneven light beams cannot be solved by merely increasing the density of the LEDs. Providing an improved structure still is needed.